1. Field of the Invention
The present invention relates to a sheet cutting apparatus in which a portion of a cutting blade to be used for cutting a sheet, a sheet stack, etc. is varied to make it possible to uniformly use the cutting blade, a sheet aftertreatment apparatus equipped with the sheet cutting apparatus, and an image forming apparatus whose apparatus main body has the sheet aftertreatment apparatus as one of its components.
2. Related Background Art
Conventionally, a sheet cutting apparatus which cuts a sheet, a sheet stack, etc. (hereinafter referred to as “sheets to be cut”) with a cutting blade is provided in a sheet aftertreatment apparatus as one of the components of the sheet aftertreatment apparatus which is provided in the apparatus main body of an image forming apparatus. The sheet aftertreatment apparatus binds sheets discharged from the apparatus main body of the image forming apparatus into a stack, and then performs glue binding or saddle-stitch/buckle binding. To align the end surface of the bound sheets, an end portion of the sheet stack is cut off by the sheet cutting apparatus (Japanese Patent Application Laid-open No. 2003-292230). The sheet cutting apparatus may cut not only a sheet stack but also a single sheet. In other words, the sheet cutting apparatus is adapted to cut different forms of sheets to be cut, which may be a sheet stack or a single sheet. The image forming apparatus is an apparatus for forming an image on a sheet, and may be a copying machine, a printer, a facsimile apparatus, a multifunctional apparatus composed of those apparatuses, etc.
In the conventional sheet cutting apparatus, regardless of the size of the sheets to be cut, sheets are always fed to the same position and cut there. Thus, the cutting blade is not uniformly used over its entire length but includes a portion always used for cutting regardless of the size of the sheets to be cut, and a portion not used for cutting according to the size of the sheets to be cut, resulting in a variation in wear. As a result, when its portion constantly used has lost its sharpness, the cutting blade must be replaced by a new one even if it includes a portion which is not much used and, consequently, cuts well. Thus, the cutting blade cannot be used for a long period of time.
Further, the sheet aftertreatment apparatus equipped with the sheet cutting apparatus requires temporary suspension of after-treatment operation in order to replace the cutting blade, resulting in a rather low operating efficiency (availability ratio).
Furthermore, due to the low operating efficiency (availability ratio) of the sheet aftertreatment apparatus, the conventional image forming apparatus equipped with the sheet aftertreatment apparatus having such a sheet cutting apparatus exhibits a rather low operating efficiency (availability ratio).